Field
The present invention relates to a method for transmitting and receiving contents, and more specifically to a method for transmitting and receiving contents including tracking information to prevent illegal duplication.
Background
Recently, the number of users streaming contents on the web is increasing. Streaming contents refers to a transmission method for enabling data of the content provided by a supplier to be received by a client in real-time. In this regard, streaming service can be divided largely into a stage of preparing target content to be streamed and a service stage of streaming the content upon request of a user or a terminal. Service providers apply a Digital Right Management (DRM) technology to prevent leakage and duplication of content by third parties. A DRM encryption technology is applied while content is still in a compression state through one of a plurality of video compression encoders. In other words, various contents are compressed first in a content preparation stage and undergo an encryption process. Afterwards, the encrypted content is transmitted in the form of a file at the service stage.
However, the DRM technology is inadequate to block the leakage and duplication of decrypted content. In this regard, a forensic watermarking technology is needed, which is capable of reversely tracking a leakage path of the corresponding content. Forensic watermarking inserts forensic marks into target content by modifying RGB values of the content and saving the modified RGB values while the target content is in a decompressed state. Therefore, DRM encryption is possible only when forensic watermarks are inserted into target content before it is compressed.
Forensic watermarks can be inserted according to the following two forms: inserting session information (information of a user and a terminal) on a server or at a terminal in real-time.
However, the method for inserting at the terminal in real-time posed a problem that forensic mark functions should be added to all of the receiving terminals, and the method for inserting on the server in real-time was incapable of securing the efficiency of real-time and simultaneous connection. Thus, the conventional technology poses difficulty in transmitting high-quality contents in real-time, and can play only a limited number of streams even with high performance hardware.
This leads to an improved technique for inserting forensic marks on the server in real-time, for example a technique for preparing in advance first contents into which forensic watermarks of a first pattern (Pattern 1) are inserted and second contents into which forensic watermarks of a second pattern (Pattern 2) are inserted other than the original contents, and combining them in real-time based on the session information at the time of transmitting the contents.
However, the technique such as the above should generate and save all of the contents including the first and second patterns in advance, and thus needs more than double storage space. And since the contents differ depending on each of the sessions, a content delivery network (CDN) cannot be used, it is unable to transmit contents efficiently.